Heat Pump Systems and Methods

Abstract

Provided herein are methods and systems for generating steam. The methods may comprise circulating a first working fluid through a first heat pump cycle, circulating a second working fluid through a second heat pump cycle, and transferring heat from said first working fluid to said second working fluid in a heat exchanger coupled to the first heat pump cycle and the second heat pump cycle. In some embodiments, the first heat pump cycle receives heat from an ambient air stream.

1 . A method for generating steam using a cascading heat pump system comprising a heat transfer fluid cycle, a first heat pump cycle, and a second heat pump cycle, the method comprising:
 circulating a heat transfer fluid through the heat transfer fluid cycle, wherein:
 the heat transfer fluid cycle comprises a first heat exchanger, an additional heat exchanger, a second heat exchanger, and a circulation pump circulating the heat transfer fluid through at least one of the additional heat exchanger and the second heat exchanger, 
 the additional heat exchanger is thermally coupled to a heat source subunit and transfers heat from the heat source subunit to the heat transfer fluid, and 
 the second heat exchanger receives the heat transfer fluid and a first working fluid to transfer heat from the heat transfer fluid to the first working fluid; 
   circulating the first working fluid through the first heat pump cycle, wherein:
 the first heat pump cycle comprises the second heat exchanger, a first compressor, a third heat exchanger, and a first expansion valve, 
 the first compressor compresses the first working fluid received from the second heat exchanger and delivers the first working fluid to the third heat exchanger, 
 the third heat exchanger receives the first working fluid and a second working fluid and transfers heat from the first working fluid to the second working fluid, and 
 the first expansion valve expands the first working fluid received from the third heat exchanger and delivers the first working fluid to the second heat exchanger; and 
   circulating the second working fluid through the second heat pump cycle, wherein:
 the second heat pump cycle comprises the third heat exchanger, a second compressor, a heated-fluid generator, and a second expansion valve, 
 the second compressor compresses the second working fluid received from the third heat exchanger and delivers the second working fluid to the heated-fluid generator, 
 the steam generator receives the second working fluid and a feed stream comprising water and transfers heat from the second working fluid to the feed stream thereby generating the steam, and 
 the second expansion valve expands the second working fluid received from the steam generator and delivers the second working fluid to the third heat exchanger. 
   
     
     
         2 . The method of  claim 1 , wherein the first heat exchanger receives an ambient air stream and transfers heat from the ambient air stream to the heat transfer fluid. 
     
     
         3 . The method of  claim 1 , wherein:
 the heated-fluid generator is a steam generator, and   the heated fluid is steam.   
     
     
         4 . The method of  claim 1 , wherein:
 the heated-fluid generator is a hot-water generator, and   the heated fluid is hot water.   
     
     
         5 . The method of  claim 1 , wherein the heat source subunit is selected from the group consisting of a (i) refrigeration system, (ii) a geothermal heat source, (iii) a waste heat stream from a process, a wastewater or waste heat stream from a heat system, a power system, or a combined heat and power system, (iv) a carbon capture process, (v) a body of water, (vi) a district energy system, (vii) a solar thermal heat source, and (viii) a nuclear reactor. 
     
     
         6 . The method of  claim 5 , wherein the heat source subunit is the refrigeration system. 
     
     
         7 . The method of  claim 1 , wherein the additional heat exchanger and the first heat exchanger form a vapor compression cycle further comprising an additional compressor and an additional expansion valve. 
     
     
         8 . The method of  claim 1 , wherein the additional heat exchanger is connected in series or in parallel with the first heat exchanger and receives a subunit fluid, and transferring heat from the subunit fluid to the heat transfer fluid. 
     
     
         9 . The method of  claim 8 , wherein the subunit fluid comprises one or more of ammonia (NH 3 ), water (H 2 O), carbon dioxide (CO 2 ) pentane (C 5 H 12 ), butane (C 4 H 10 ), isobutane (HC(CH 3 ) 3 ), propane (C 3 H 8 ), or propene (C 3 H 6 ), a hydrofluoro-olefin (HFO) fluid, and a hydrofluoro-chlorine (HFC) fluid, a hydrochlorofluoro-olefin (HCFO) fluid, or a natural refrigerant. 
     
     
         10 . The method of  claim 1 , further comprising compressing the steam using a steam compressor. 
     
     
         11 . The method of  claim 1 , further comprising cooling at least one of the first compressor and the second compressor using a motor coolant stream, comprising a corresponding one of the first working fluid or the second working fluid. 
     
     
         12 . The method of  claim 11 , further comprising cooling the motor coolant stream, prior to flowing the motor coolant stream into at least one of the first compressor and the second compressor, using one or more of (i) a glycol cooler, (ii) an air cooler, or (iii) a vapor compression cycle. 
     
     
         13 . The method of  claim 1 , wherein:
 the first heat exchanger is one of multiple air-source heat exchangers, connected in parallel within each other in the heat transfer fluid cycle, and   the method comprising defrosting one of the multiple air-source heat exchangers while operating the first heat exchanger.   
     
     
         14 . The method of  claim 13 , wherein defrosting the one of the multiple air-source heat exchangers is performed using an electric resistance heater embedded in or on one or more coils of one of the multiple air-source heat exchangers. 
     
     
         15 . The method of  claim 13 , wherein defrosting the one of the multiple air-source heat exchangers is performed by:
 heating the heat transfer fluid, thereby producing a heated heat transfer fluid, and   circulating the heated heat transfer fluid through the one of the multiple air-source heat exchangers.   
     
     
         16 . The method of  claim 15 , wherein heating the heat transfer fluid is performed using the first working fluid or the second working fluid and a heat transfer fluid heater receiving the first working fluid from the first compressor or receiving the second working fluid from the second compressor and transferring heat to the heat transfer fluid, thereby producing the heated heat transfer fluid. 
     
     
         17 . The method of  claim 16 , wherein the heat transfer fluid heater is connected in parallel with the second heat exchanger. 
     
     
         18 . The method of  claim 16 , wherein the heat transfer fluid heater is connected in series and upstream from the second heat exchanger. 
     
     
         19 . The method of  claim 16 , wherein the heat transfer fluid cycle comprises a set of valves for selectively controlling flow of the heated heat transfer fluid from the heat transfer fluid heater or the heat transfer fluid from the second heat exchanger through each of the multiple air-source heat exchangers. 
     
     
         20 . The method of  claim 1 , wherein the first heat pump cycle comprises a first economizer that:
 splits the first working fluid from the third heat exchanger into a first sub-stream and a second sub-steam,   passes the first sub-stream through a first-economizer expansion valve,   transfers heat from the second sub-steam to the first sub-stream received from the first-economizer expansion valve,   directs the first sub-stream to the first compressor, and   direct the second sub-steam to the second heat exchanger.